1. Field of the Invention
Aspects of the present invention relates to a transmitting apparatus and method and, more particularly, to a transmitting apparatus and method in a multi-user multiple-input and multiple-output (MIMO) system in a mobile communication system.
2. Description of the Related Art
A MIMO transmission method is one technique of increasing a communication speed between wireless devices. The MIMO transmission method is based on input/output of signals using multiple antennas and simultaneously transmits a plurality of transmission data signals using the multiple antennas at the same time. Accordingly, the number of channels through which data signals can be simultaneously transmitted increases, and thus the quantity of information that can be transmitted per unit time can be increased by the increased number of channels. Furthermore, the MIMO transmission method improves communication speed without increasing an occupied frequency band.
However, a plurality of modulated signals having a carrier component of the same frequency is simultaneously transmitted, and thus a receiver needs a way to split mixed modulated signals. Accordingly, the receiver estimates a channel matrix representing transmission characteristics of a wireless transmission path and separates a transmission signal corresponding to each sub-stream from a received signal on the basis of the channel matrix. The channel matrix is estimated using a pilot symbol or the like.
In order to sufficiently remove the influence of noise added to transmission data in a transmission path or interference generated between sub-frames to reproduce a correct transmission signal for each sub-stream, a special idea is required. Recently, various techniques for MIMO signal detection have been developed. In particular, a multi-user MIMO system including a plurality of communication devices capable of performing MIMO signal transmission is being developed. The multi-user MIMO system employs a method of detecting a signal using a minimum mean squared error (MMSE), for example. This method improves transmission characteristics in such a manner that a receiver calculates a signal power-to-interference plus noise power ratio (SINR) after MMSE detection and feeds the SINR to a transmitter and a transmission control parameter is set based on the SINR after MMS detection. Moreover, a receiver of the multi-user MIMO system may use a method of improving transmission characteristic over the MMSE detection method, for example, a maximum likelihood (ML) detection method.